2MASS J12195156+3128497
2MASS J12195156+3128497 is a rapidly-rotating brown dwarf of spectral class L8, located in the constellation Coma Berenices about 66 light-years from Earth. With a photometrically measured rotation period of 1.14 hours, it is one of the fastest-rotating known brown dwarfs announced by a team of astronomers led by Megan E. Tannock in March 2021. With a rotational velocity of about, it is approaching the predicted rotational speed limit beyond which it would break apart due to centripetal forces. As a consequence of its rapid rotation, the brown dwarf is slightly flattened at its poles to a similar degree as Saturn, the most oblate planet in the Solar System. Its rapid rotation may enable strong auroral radio emissions via particle interactions in its magnetic field, as observed in other known rapidly-rotating brown dwarfs.
Discovery
2MASS J1219+3128 was first catalogued as a point source in June 2003 by the Two Micron All-Sky Survey organized by the University of Massachusetts Amherstand the Infrared Processing and Analysis Center under the California Institute of Technology. It was discovered to be a brown dwarf of the spectral class L8 by K. Chiu and collaborators, based on near-infrared observations obtained from the Sloan Digital Sky Survey at Apache Point Observatory in New Mexico, United States. Their discovery and classification of 71 L and T dwarfs including 2MASS J1219+3128 was published in The Astronomical Journal in June 2006.